It is known to provide a height adjustment mechanism for a telescopic leg supported work surface including a counterbalance mechanism for providing a counterbalance force opposing a downward force tending to lower the work surface, a lock mechanism for releasably retaining the work surface in a desired vertical position, and a manual operator for selectively releasing the lock mechanism to permit vertical movement of the table top, while preventing operation of the lock mechanism if the counterbalance force and the downward force are out of balance, as evidenced by U.S. Pat. No. 5,706,739.
It is also known to employ a mechanical lock of the type disclosed in U.S. Pat. No. 4,577,730 to releasably lock a 20 work surface against vertical movement, as evidenced by U.S. Pat. No. 5,704,299.